1. Field of the Invention
This invention relates to a process for preparing functionalized alkynes having internal triple bonds.
2. Description of the Related Art
The preparation of acetylenic compounds by bromination followed by dehydrobromination is known in the art. Fatty alkynes such as stearolic acid, palmitolic acid, behenolic acid, and ricinstearolic acid have been prepared from the corresponding olefinic fatty acids by bromination and dehydrohalogenation with alcoholic potassium hydroxide (Ann., 1866, 140, 39; Ann., 1867, 143, 27; Ann., 1867, 143, 41; Ann., 1865, 135, 226). Aqueous potassium and sodium hydroxides have also been used along with a polyethylene glycol catalyst in the dehydrohalogenation of internal vicinal dibromohydrocarbons to acetylenic hydrocarbons. (J. Org. Chem., 47, 2493, 1982). Aqueous sodium hydroxide has similarly been used in the presence of tetrabutyl ammonium bisulfate to eliminate vicinal dibromo-hydrocarbons to acetylenic hydrocarbons (Tetrahedron Letters, 1976, 4723). Solid potassium hydroxide in the presence of phase transfer catalysts such as quaternary amines (Aliquat 336, tetraoctyl ammonium bromide) or crown ethers (18-crown-6) has been used to accomplish the dehydrohalogenation of vicinal dibromo hydrocarbons (Tetrahedron, 1981, 37, 1653). None of the prior art methods provides a process for preparing alkynes that uses an inexpensive base such as potassium or sodium hydroxide in the solid state in the presence of polyethylene glycols to produce alkynes. None of the prior art methods provides a process for preparing alkynes that utilizes solid sodium hydroxide in the presence of a phase transfer catalyst for dehydrohalogenation to yield an alkyne product that is easily separated from the reaction mixture.